KABUL — A Taliban suicide bomber struck near a Kabul police complex Monday, killing at least 20 police officers and wounding 29 people, Afghan officials said, in the latest of a rapid-fire series of militant attacks on the capital this year.

The attack came as the US military issued a grim confirmation of the war’s toll on the Afghan security forces, saying that casualties among Afghan soldiers and policemen in 2015 were up by almost a third. That set a record from the year before — a casualty rate so high that some officials described it then as unsustainable.

Sediq Sediqqi, a spokesman for the Afghan interior ministry, said the attack Monday happened near the gate of the National Civil Order Police. Witnesses said the bomber had walked up to a line of visitors waiting for a security check and detonated his explosives.

A Taliban spokesman, Zabihullah Mujahid, claimed responsibility for the attack in a statement, saying the bomber targeted the facility as a large group of police officers was leaving.

“You see that tree? The branches are covered in flesh and blood,’’ said Ahmad Parwiz, who sells fried dough across the street from the National Civil Order Police. “There were a lot of visitors queued up to go inside when the explosion happened. Thank God we weren’t hurt on this side of the road.’’

Intense Taliban offensives that are carrying on through the winter, including the string of bombings in Kabul, have Afghan and Western officials increasingly worried about the pressure on the Afghan security forces.

New York Times